package user;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

@WebServlet(name = "CaptchaServlet")
public class CaptchaServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获得验证码集合的长度

        String codeChars = "abcdefghkmnprstuvwxyzABCDEFGHKMNPRSTUVWXYZ23456789";
        int charsLength = codeChars.length();

        //下面3条记录是关闭客户端浏览器的缓冲区

        //这3条语句都可以关闭浏览器的缓冲区，但是由于浏览器的版本不同，对这3条语句的支持也不同

        //因此，为了保险起见，同时使用这3条语句来关闭浏览器的缓冲区

        response.setHeader("ragma", "No-cache");

        response.setHeader("Cache-Control", "no-cache");

        response.setDateHeader("Expires", 0);

        //设置图形验证码的长和宽

        int width = 130, height = 50;

        BufferedImage image = new BufferedImage(width,height, BufferedImage.TYPE_INT_RGB);

        Graphics g = image.getGraphics(); //获得用于输出文字的Graphics对象

        Random random = new Random();

        g.setColor(getRandomColor(180, 250));

        g.fillRect(0, 0, width, height);

        g.setFont(new Font("Times New Roman",Font.ITALIC,height));

        g.setColor(getRandomColor(120, 180));

        //用户保存最后随机生成的验证码

        StringBuilder validationCode = new StringBuilder();

        //验证码的随机字体

        String[] fontNames = {"Times New Roman","Book antiqua","Arial"};

        //随机生成4个验证码
        //String code = "";
        for(int i = 0; i < 4; i++){

            //随机设置当前验证码的字符的字体

            g.setFont(new Font(fontNames[random.nextInt(3)], Font.ITALIC,height));

            //随机获得当前验证码的字符

            char codeChar = codeChars.charAt(random.nextInt(charsLength));
            //code += codeChar;

            validationCode.append(codeChar);

            //随机设置当前验证码字符的颜色

            g.setColor(getRandomColor(10, 100));

            //在图形上输出验证码字符，x和y都是随机生成的

            g.drawString(String.valueOf(codeChar), 20*i + random.nextInt(7), height-random.nextInt(6));

        }

        int x1, y1, x2, y2;
        int lineNum = random.nextInt(4) + 4;
        for (int i = 0; i < lineNum; i++) {
            x1 = random.nextInt(width/2);
            y1 = random.nextInt(height/2);
            x2 = random.nextInt(width);
            y2 = random.nextInt(height);
            g.setColor(getRandomColor(10, 100));
            g.drawLine(x1, y1, x2, y2);
        }

        //System.out.println(code);

        //获得HttpSession对象

        HttpSession session = request.getSession();

        //设置session对象5分钟失效

        session.setMaxInactiveInterval(5*60);

        //将验证码保存在session对象中,key为validation_code

        session.setAttribute("validation_code", validationCode.toString());

        //关闭Graphics对象

        g.dispose();

        OutputStream outS = response.getOutputStream();

        ImageIO.write(image, "JPEG", outS);
    }

    //图形验证码的字符集，系统将随机从这个字符串中选择一些字符作为验证码

    //返回一个随机颜色

    private static Color getRandomColor(int minColor, int maxColor){

        Random random = new Random();

        if(minColor > 255){

            minColor = 255;

        }

        if(maxColor > 255){

            maxColor = 255;

        }

        //获得r的随机颜色值

        int red = minColor + random.nextInt(maxColor-minColor);

        //g

        int green = minColor + random.nextInt(maxColor-minColor);

        //b

        int blue = minColor + random.nextInt(maxColor-minColor);

        return new Color(red,green,blue);

    }
}
